CLIO BOREALIS. 



553 



these little beings in those regions where they are common, that the 

 surface of the sea seems literally alive with their gambollings ; and thus 

 the store of provisions necessary to render the waters of the ocean 

 habitable to animals of higher grade in the scale of life is still further 

 increased. The great character that distinguishes the members of the 

 class upon the investigation of which we are now entering is derived 

 from the structure of their organs of locomotion. These are only 

 adapted for swimming, and consist of two broad and fleshy expansions, 

 attached like a pair of wings to the sides of the neck, and forming 

 moveable fins enabling the little beings to dance merrily among the 

 foamy waves, now sinking, and again rising to the surface, until some 

 passing whale, opening its enormous jaws, engulfs multitudes of such 

 tiny victims, and hence derives the materials for its subsistence. 



(1479.) Several distinct genera of Pteropoda have been established 

 by zoologists, and some important modifications have been detected in 

 their organization, although in all of them the lateral ala3 form the in- 

 struments of progression. 



(1480.) The Clio borealis, anatomized by Cuvier*, and more recently 

 and completely investigated by Professor Eschricht of Copenhagen f, is 

 one of the species best known, as well as most abundantly met with ; it 

 is therefore by a description of this Pteropod that we shall proceed to 

 introduce the reader to the general facts connected with the history of 

 the animals under consideration. 



Fig. 277. 





Clio borealis ; represented at A in a state of repose, while B, C exhibit the various external 

 appendages fully protruded : a a, wing-like oars ; b, hood retracted ; g, bladder-like organ ; 

 A, penis ; k, tentacle ; o, globular protuberances ; s s, conical appendages. 



(1481.) The body of the Clio is about an inch in length, of an oblong 

 shape, and terminating posteriorly in a point; while at the opposite 

 extremity there is a little head supported upon a short neck, and 



* Memoire sur le Clio borealis. 



t Anatomische Untersuchungen iiber die Clione borealis, von D. F. Eschricht. 

 Kopenhagen, 1838, 4to. 



